Ecosystems, Ecosystem Services, and Biodiversity

Ecosystem Services at Risk

The resources and services that people depend on for their livelihoods, sustenance, protection, and well-being are jeopardized by the impacts of climate change on ecosystems. Fundamental changes in agricultural and fisheries production, the supply of clean water, protection from extreme events, and culturally valuable resources are occurring.

Climate change is affecting the availability and delivery of ecosystem services to society through altered provisioning, regulating, cultural, and supporting services.95

A reduced supply of critical provisioning services (food, fiber, and shelter) has clear consequences for the U.S. economy and national security and could create a number of challenges for natural resource managers.104 Although an extended growing season resulting from phenological shifts may have positive effects on the yield and prices of particular crops,173 net changes to agricultural productivity will vary regionally (Figure 7.6) and will be affected by other climate change impacts, such as drought and heat stress.174,175 In addition, early springs with comparatively late (but climatically normal) frosts can directly affect plant growth and seed production and indirectly disrupt ecosystem services such as pollination. By the middle of this century, early onset of spring could occur one out of every three years; however, if the date of last freeze does not change at the same rate, large-scale plant damage and agricultural losses, 176,177,178 as well as changes to natural resource markets,119 are possible. Shellfish harvests are also projected to decline significantly through the end of the century due to ocean acidification, with cumulative estimated losses of $230 million under RCP8.5 and $140 million under RCP4.5 (discounted at 3%) (see the Scenario Products section of App. 3 for more information on scenarios).104

Figure 7.6: Agricultural Productivity

Figure 7.6: The figure shows the projected percent change in the yield of corn, wheat, soybeans, and cotton during the period 2080–2099. Units represent average percent change in yields under the higher scenario (RCP8.5) as compared to a scenario of no additional climate change. Warmer colors (negative percent change) indicate large projected declines in yields; cooler colors (green) indicate moderate projected increases in yields. Source: adapted from Hsiang et al. 2017.179 Data were not available for the U.S. Caribbean, Alaska, or Hawaiʻi and U.S.-Affiliated Pacific Islands regions.

The degree to which climate change alters species’ ranges can create jurisdictional conflict and uncertainty.97 For example, fisheries management is typically done within defined boundaries and governed by local or international bodies, and terrestrial resource extraction typically occurs on private property or leased public lands with legislated boundaries.180 Local extinctions and range shifts of marine species have already been documented (Ch. 9: Oceans, KM 2), as species’ ranges shift with changing habitat and food conditions. Some species have moved out of historical boundaries and seasonal areas and into places that have no policy, management plan, or regulations in place to address their presence and related human use. Furthermore, unique life histories and genetic resources will likely be lost altogether as range shifts and the spread of invasive species interact with ecological complexity. Examples include loss of genetic diversity and the evolution of traits that increase rates of dispersal.181,182 Managers may also need to respond to an alteration in the timing of spawning and migration of fish species in order to avoid overly high levels of fish mortality.183

Some cultural ecosystem services are also at risk from climate change. By the end of the century (2090), cold water recreational fishing days are predicted to decline, leading to a loss in recreational fishing value of $1.7 billion per year under RCP4.5
and $3.1 billion per year under RCP8.5 by 2090.104 Climate change is also predicted to shorten downhill and cross-country ski seasons.104 In northwestern Wyoming and western Montana, the cross-country ski season is projected to decline by 20%–60% under RCP4.5 and 60%–100% under RCP8.5 by 2090 (Ch. 22: N. Great Plains, KM 3). Climate change also threatens Indigenous peoples’ cultural relationships with ancestral lands (Ch. 15: Tribes, KM 1). In addition, biodiversity and ecosystems are valuable to humans in and of themselves through their “existence value,” whereby people derive satisfaction and value simply from knowing that diverse and healthy ecosystems exist in the world.190 For example, a recent study found that the average U.S. household is willing to pay $33–$73 per year for the recovery or delisting of one of eight endangered or threatened species they studied.191 However, climate change could have a positive impact on recreational activities that are more popular in warmer weather. For example, demand for biking, beachgoing, and other recreational activities has been projected to increase as winters become milder.95,192

Finally, climate change is impacting supporting services, which are the services that make all other ecosystem services possible. Climate change impacts include alterations in primary production and nutrient cycling.48,193 Novel species assemblages associated with climate change can result in changes to energy and nutrient exchange (for example, altered carbon use in streams as new detritus-feeding or predator communities emerge) within and among ecological communities.193 Because supporting services underpin all other ecosystem services, climate-induced changes to these services can have profound effects on human well-being.